AT527216B1 - cell stack system for a fuel cell system - Google Patents

Abstract

The present invention relates to a cell stack system (100) for a fuel cell system, comprising a plurality of cell stacks (110), each cell stack (110) having an anode section (120) and a cathode section (130), a pipe system (50) for supplying anode feed gas (AZG) and cathode feed gas (KZG) to the cell stacks (110) and for discharging anode exhaust gas (AAG) and cathode exhaust gas (KAG) from the cell stacks (110), a distribution system (10) per cell stack (110), each distribution system (10) connecting the anode section (120) and the cathode section (130) of the corresponding cell stack (110) to the pipe system (50) in a fluid-communicating manner, and a holding device (70) for holding the cell stacks (110), the cell stacks (110) being arranged opposite the holding device (70) are movable, and wherein the holding device (70) is mechanically separated from the pipe system (50) or the distribution systems (10), wherein the cell stack system (100) has connecting elements (20) which are arranged between the holding device (70) and the cell stacks (110), wherein the connecting elements (20) are designed as rolling elements (24).

Description

Description

CELL STACKING SYSTEM FOR A FUEL CELL SYSTEM

[0001] The present invention relates to a cell stack system for a fuel cell system and in particular to a cell stack system in which cell stacks are movable relative to a holding device.

[0002] Cell stack systems for a fuel cell system are known in the prior art. Such cell stack systems have several cell stacks. The compensation of the thermal length change in these cell stack systems is typically achieved by compensation tubes, such as bellows tubes. The bellows tubes are normally radially symmetrical and are used in large numbers. These compensation tubes are repeatedly used in sections along the entire length of the pipe system. The thermal compensation via the pipe system is coupled with the fluid supply via the pipe system. The disadvantage of this solution is that the compensation tubes require very fragile and expensive high-temperature components, which lead to a higher complexity of the cell stack system and can cause a sealing problem because additional welds or flanges are required.

[0003] A cell stack system for a fuel cell system is disclosed, for example, in US 6455179 B1.

[0004] Against this background, it is an object of the present invention to at least partially eliminate the disadvantages described above. In particular, it is an object of the present invention to provide a cell stack system in which the compensation of the thermal length change is separate from the fluid supply.

[0005] The above objects are achieved by a cell stack system having the features of claim 1. Further features and details of the invention emerge from the subclaims, the description and the drawings.

[0006] Accordingly, a cell stack system for a fuel cell system is provided. The cell stack system comprises a plurality of cell stacks, each cell stack having an anode section and a cathode section, a pipe system for supplying anode feed gas and cathode feed gas to the cell stacks and for discharging anode exhaust gas and cathode exhaust gas from the cell stacks, a distribution system per cell stack, each distribution system fluidly connecting the anode section and the cathode section of the corresponding cell stack to the pipe system, and a holding device for holding the cell stacks, the cell stacks being movable relative to the holding device, and the holding device being mechanically separated from the pipe system or the distribution systems.

[0007] Because the holding device is mechanically separated from the pipe system or the distribution systems, the fluid supply can be separated from the compensation of the thermal length change. The compensation of the thermal length change is achieved by the cell stacks being movable relative to the holding devices. The pipe system and the distribution systems only fulfill the function of the fluid supply, i.e. fluid inflow and fluid outflow.

[0008] The expression "wherein the holding device is mechanically separated from the pipe system or the distribution systems" means that the holding device on the one hand and the pipe system and the distribution systems on the other hand are not directly mechanically connected to one another. There is therefore no direct mechanical connection between the holding device on the one hand and the pipe system and the distribution systems on the other. There is contact between the holding device and the cell stacks in that the cell stacks are held by the holding device. The cell stacks are movable relative to the holding device. There is also a fluid-communicating connection between the pipe system and the distribution systems and between the distribution systems and the cell stacks.

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[0009] In the present application, a fuel cell system is understood to mean a system (e.g. SOFC: Solid Oxide Fuel Cell) which has fuel cells for generating electrical energy using a fuel, or a system (e.g. SOEC: Solid Oxide Electrolyzer Cell) which has electrolysis cells for generating a fuel using electrical energy. A cell stack therefore has several fuel cells or several electrolysis cells.

[0010] The anode section of the cell stack supplies anode feed gas to all cells (fuel cells or electrolysis cells) and removes anode exhaust gas from all cells (fuel cells or electrolysis cells).

[0011] The cathode section of the cell stack supplies all cells (fuel cells or electrolysis cells) with cathode feed gas and removes cathode exhaust gas from all cells (fuel cells or electrolysis cells).

[0012] According to the invention, the cell stack system has connecting elements which are arranged between the holding device and the cell stacks. The connecting elements establish a mechanical contact between the holding device and the cell stacks. The connecting elements can be used to ensure that the cell stacks can move relative to the holding device. Alternatively, the connecting elements can be dispensed with. In this case, there is direct mechanical contact between the holding device and the cell stacks, whereby here too the cell stacks can be moved relative to the holding device.

[0013] In principle, the connecting elements can be designed as sliding elements. The sliding elements slide on the holding device. The sliding elements can be mechanically firmly connected to the cell stacks.

[0014] In principle, several sliding element fixing elements can also be provided, each sliding element being mechanically firmly connected to a distribution system by means of a sliding element fixing element. Advantageously, the forces that act during the thermally induced movement of a cell stack are then not transmitted via the seal between the cell stack and the distribution system. The force for the movement is essentially transmitted via one or more sliding elements, in particular two sliding elements, between the cell stack and the distribution system. Furthermore, the sliding element fixing elements can also consist of several parts, e.g. if the distribution system also has several sections.

[0015] The holding device can be designed as a rail system, the rail system having rails and the sliding elements being designed to slide on the rails. The rail system can be used to provide a technologically simple system that is less prone to errors. In particular, the rail system can have two rails.

[0016] According to the cell stack system according to the invention, however, the connecting elements are designed as rolling elements. The friction when rolling is in principle lower than when sliding. The rolling elements can therefore be used to reduce the friction compared to sliding elements. The cell stacks can therefore be moved particularly easily relative to the holding device.

[0017] According to a further embodiment of the cell stack system, the rolling elements are designed as balls. Advantageously, balls are particularly stable in terms of their shape, can bear high loads and are easy to manufacture.

[0018] According to a further embodiment of the cell stack system, the rolling elements are designed as cylinders. In particular, the cylinders can be circular cylinders. Rolling elements with a circular cylindrical shape are also easy to manufacture.

[0019] According to a further embodiment of the cell stack system, each connecting element has several elastic elements. Due to the elastic elements, the cell stacks are movable relative to the holding device. In particular

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the connecting element has between 2 and 5, between 2 and 8, between 2 and 10 or between 2 and 20 elastic elements. The elastic elements can be, for example, thin plates. The thin plates can comprise metal. Such plates can bend by a few millimeters. This allows a displacement of the cell stacks relative to the holding device by a few millimeters. In particular, this allows a displacement of the cell stacks relative to the holding device of 1 mm to 3 mm, 1 mm to 5 mm, 1 mm to 7 mm or 1 mm to 10 mm.

[0020] According to a further embodiment of the cell stack system, the pipe system extends in a longitudinal direction. In this case, “the pipe system extends in a longitudinal direction” means that the pipe system preferably extends along a straight line. Alternatively, the longitudinal direction can also have one or more bends. With a pipe system extending in the longitudinal direction, the number of cell stacks can be increased particularly easily.

[0021] According to a further embodiment of the cell stack system, a single section of the pipe system is designed as a bellows tube at a fluid inlet of the pipe system. If the pipe system has several pipes, then all pipes of the pipe system can have a single section which is designed as a bellows tube. The expression "at a fluid inlet" means in the area of the fluid inlet. A bellows tube is a pipe whose pipe wall has a wave-like structure which can expand and contract in the pipe direction.

[0022] According to a further embodiment of the cell stack system, the pipe system has at least one anode feed pipe, at least one cathode feed pipe, at least one anode discharge pipe and at least one cathode discharge pipe. Each distribution system has an anode feed section for feeding anode feed gas from the anode feed pipe to the anode section, an anode discharge section for discharging anode exhaust gas from the anode section to the anode discharge pipe, a cathode feed section for feeding cathode feed gas from the cathode feed pipe to the cathode section and a cathode discharge section for discharging cathode exhaust gas from the cathode section to the cathode discharge pipe.

[0023] Accordingly, the pipe system has four or more pipes. The pipe system can also be connected in a fluid-communicating manner to cell stacks arranged in two rows. In this case, the pipe system can in particular have two anode feed pipes or two cathode feed pipes.

[0024] According to a further embodiment of the cell stack system, the cell stack system has a holding device fixing element, wherein the pipe system is mechanically firmly connected to the holding device at a holding device fixing point at a pipe system fixing point by means of the holding device fixing element. Because the pipe system is firmly connected to the holding device at the holding device fixing point, the holding device fixing point represents the reference point for the thermally induced linear expansion of the cell stack system. The cell stacks are movable relative to the holding device, as described above and below in the text. In particular, the cell stacks are movable in the longitudinal direction relative to the holding device fixing point. The pipe system, which is mechanically firmly connected to the holding device at the holding device fixing point, can also expand in the longitudinal direction with the holding device fixing point as a fixed point in the longitudinal direction, relative to this fixed point due to thermal factors. At the fluid inlet, the thermally induced change in length of the pipe system is made possible by the bellows tube. The pipe system end can be provided without a fluid connection. The fluid outlet can be on the side of the fluid inlet. In this case, in the event of a thermally induced change in length, there are no restrictions on the side of the pipe system that has the pipe system end.

[0025] According to a further embodiment of the cell stack system, the pipe system has a pipe system start, a pipe system end and a pipe system length.

Pipe system fastening point is at least 30% of the pipe system length, at least 35% of the pipe system length, at least 40% of the pipe system length or at least 45% of the pipe system length away from the pipe system start and from the pipe system end. In particular, the pipe system fastening point is arranged essentially in the middle of the pipe system. Because the pipe system fastening point and the holding device fastening point, which represents the reference point for the thermal expansion, are firmly connected to one another and the pipe system fastening point is arranged as centrally as possible in the pipe system, there is not too great a difference in the thermally induced change in length of the pipe system in both directions of the pipe system.

[0026] Further advantages, features and details of the invention emerge from the following description, in which embodiments are described in detail with reference to the drawings. They show:

[0027] Fig. 1 is a schematic view of a cell stack system; [0028] Fig. 2 is a sectional view of the cell stack system of Fig. 1 along the line II-II;

[0029] Fig. 3 is a schematic detailed representation of a distribution system and a pipe system;

[0030] Fig. 4 is a schematic view of a cell stack system according to the invention; and

[0031] Fig. 5 is a schematic view of a cell stack system in a further embodiment not according to the invention.

[0032] Fig. 1 shows a schematic view of a cell stack system 100. The cell stack system 100 can be used as part of a fuel cell system. The cell stack system 100 has several cell stacks 110, a pipe system 50, a distribution system 10 per cell stack 110 and a holding device 70. Each cell stack comprises an anode section 120 and a cathode section 130. The pipe system 50 serves to supply anode feed gas AZG and cathode feed gas KZG to the cell stacks 110 and to discharge anode exhaust gas AAG and cathode exhaust gas KAG from the cell stacks 110. Each distribution system 10 connects the anode section 120 and the cathode section 130 of the corresponding cell stack 110 in fluid communication with the pipe system 50.

[0033] The holding device 70 serves to hold the cell stacks 110. The cell stacks 110 are movable relative to the holding device 70. Furthermore, the holding device 70 is arranged mechanically separated from the pipe system 50 or the distribution systems 10, i.e. there is no direct mechanical connection between the holding device 70 on the one hand and the pipe system 50 and the distribution systems 10 on the other.

[0034] Due to the mechanical separation of the holding device 70 on the one hand and the pipe system 50 and the distribution systems 10 on the other hand, the fluid supply of the cell stack system 100 can be separated from the compensation of the thermal length change of the cell stack system 100. The compensation of the thermal length change of the cell stack system 100 is achieved by the relative mobility of the cell stacks 110 with respect to the holding device 70. In contrast, the pipe system 50 and the distribution systems 10 fulfill the function of supplying anode feed gas AZG and cathode feed gas KZG and the function of discharging anode exhaust gas AAG and cathode exhaust gas KAG.

[0035] Furthermore, Fig. 1 shows connecting elements 20 which are designed as sliding elements 22. The sliding elements 22 are arranged between the holding device 70 and the cell stacks 110. The sliding elements 22 are mechanically firmly connected to the cell stacks 110. The sliding elements 22 can slide on the holding device 70 in order to ensure the relative mobility of the cell stacks 110 to the holding device 70. Alternatively, there is no fixed connection between the sliding elements 22 and the cell stacks 110.

[0036] The holding device 70 can be designed as a rail system 80. The rail system 80 comprises several rails, in particular two rails. The sliding elements 22 are designed to slide on the rails.

[0037] As can be seen in Fig. 1, the distribution systems 10 establish a fluid-communicating connection between the pipe system 50 and the cell stacks 110. The distribution systems 10 are guided through recesses 12 in the holding device 70. The pipe system 50 also extends in a longitudinal direction 52. With such a course of the pipe system 50, the number of cell stacks 110 of the cell stack system 100 can be easily increased without major changes having to be made to the cell stack system 100.

[0038] The cell stack system 100 can have a holding device fixing element 40. The holding device fixing element 40 establishes a mechanically fixed connection from a pipe system fastening point 42 of the pipe system 50 to a holding device fastening point 44 of the holding device 70. The holding device fastening point 44 of the holding device 70 thus represents a reference point for the thermally induced change in length of the cell stack system 100. The cell stacks 110 can be displaced by means of the sliding elements 22 in the longitudinal direction 52 in both directions relative to the holding device fastening point 44. The pipe system 50 can also realize a thermally induced change in length in the longitudinal direction 52 in both directions relative to the holding device fastening point 44, since the pipe system is connected to the holding device 70 at the holding device fastening point 44 of the holding device 70.

[0039] At a fluid inlet 54 of the pipe system 50, a single section of the pipe system 50 can be designed as a bellows tube 56. The bellows tube 56 allows a thermally induced change in length of the pipe system 50 in the longitudinal direction 52 without causing problems with additional connections at the fluid inlet 54.

[0040] As shown in Fig. 1, the pipe system 50 has a pipe system start 46, a pipe system end 48 and a pipe system length L. The pipe system attachment point 42 is preferably arranged essentially in the middle of the pipe system. In any case, the pipe system attachment point 42 is at least 30% of the pipe system length L, at least 35% of the pipe system length L, at least 40% of the pipe system length L or at least 45% of the pipe system length L from the pipe system start 46 and the pipe system end 48. This ensures that the two sides of the pipe system 50 to the right and left of the pipe system attachment point 42 do not have too different thermally induced length changes in the longitudinal direction 52.

[0041] Fig. 2 shows a schematic sectional view of the cell stack system 100 of Fig. 1 along the line II-II. Shown are the cell stack 110, the distribution system 10, the pipe system 50, two connecting elements 20, which are designed as sliding elements 22, the holding device 70, which can be designed as a rail system 80, and two sliding element fixing elements 30. The two sliding elements 22 are mechanically firmly connected to the distribution system 10 by means of the two sliding element fixing elements 30. Due to the two sliding element fixing elements 30, the force which is caused by the thermally induced change in length of the cell stack system 100 and which acts between the cell stack 110 and the distribution system 10 does not need to be transmitted via the seal between the cell stack 110 and the distribution system 10. Instead, the force can be transmitted via the sliding elements 22 between the cell stack 110 and the distribution system 10.

[0042] If the distribution system 10 has multiple sections, then the two sliding element fixing elements 30 may have multiple elements to mechanically connect the multiple sections to the two sliding elements 22.

[0043] The pipe system 50 shown in Fig. 2 may have several pipes and the distribution system shown in Fig. 2 may have several sections, as shown in Fig. 3, for example.

[0044] Fig. 3 shows a schematic detailed representation of a distribution system 10 with several sections 122, 124, 132, 134 and a pipe system 50 with several pipes 62, 64, 66, 68. The pipe system 50 has an anode feed pipe 62, a cathode feed pipe 64, an anode discharge pipe 66 and a cathode discharge pipe 68. The distribution system 10 has an anode

a feed section 122 for feeding anode feed gas AZG from the anode feed pipe 62 to the anode section 120, an anode discharge section 124 for discharging anode exhaust gas AAG from the anode section 120 to the anode discharge pipe 66, a cathode feed section 132 for feeding cathode feed gas KZG from the cathode feed pipe 64 to the cathode section 130, and a cathode discharge section 134 for discharging cathode exhaust gas KAG from the cathode section 130 to the cathode discharge pipe 68.

[0045] Fig. 4 shows a schematic view of a cell stack system 100 according to the invention. Only the differences from the cell stack system 100 shown in Fig. 1 are discussed. As shown in Fig. 4, the connecting elements 20 are designed as rolling elements 24. The cell stacks 110 can be movably mounted relative to the holding device 70 by means of the rolling elements 24. In particular, the rolling elements 24 can be designed as cylinders 28. The cylinders 28 are preferably circular cylinders. Alternatively, the rolling elements 24 can be designed as balls 26.

[0046] Fig. 5 shows a schematic view of a cell stack system 100 in a further embodiment. Only the differences from the cell stack system 100 shown in Fig. 1 are discussed. As shown in Fig. 5, the connecting elements 20 have a plurality of elastic elements 36. The cell stacks 110 can be movably mounted relative to the holding device 70 by means of the elastic elements 36. The elastic elements can in particular have thin metal plates.

REFERENCE SYMBOL LIST

10 distribution system

12 recess

20 connecting element

22 sliding element

24 rolling elements

26 balls

28 cylinders

30 sliding element fixing element

36 elastic elements

40 Holding device fixing element 42 Pipe system fastening point 44 Holding device fastening point 46 Pipe system start

48 pipe system end

50 pipe system

52 longitudinal direction

54 fluid inlet

56 bellows tube

62 anode feed pipe

64 cathode feed tube

66 anode discharge pipe

68 cathode discharge tube

70 holding device

80 rail system

100 cell stack system

110 cell stacks

120 anode section

122 Anode supply section 124 Anode discharge section 130 Cathode section

132 Cathode supply section 134 Cathode discharge section AZG Anode supply gas

AAG — anode exhaust gas

KZG cathode supply gas KAG cathode exhaust gas

L pipe system length

Claims (8)

patent claims 1. Cell stack system (100) for a fuel cell system, comprising a plurality of cell stacks (110), each cell stack (110) having an anode section (120) and a cathode section (130), a pipe system (50) for supplying anode feed gas (AZG) and cathode feed gas (KZG) to the cell stacks (110) and for discharging anode exhaust gas (AAG) and cathode exhaust gas (KAG) from the cell stacks (110), a distribution system (10) per cell stack (110), each distribution system (10) connecting the anode section (120) and the cathode section (130) of the corresponding cell stack (110) to the pipe system (50) in a fluid-communicating manner, a holding device (70) for holding the cell stacks (110), the cell stacks (110) being movable relative to the holding device (70), and the holding device (70) being mechanically separated from the pipe system (50) or the distribution systems (10), the cell stack system (100) having connecting elements (20) which are arranged between the holding device (70) and the cell stacks (110), characterized in that the connecting elements (20) are designed as rolling elements (24). 2, Cell stack system (100) according to claim 1, characterized in that the rolling elements (24) are designed as balls (26). 3. Cell stack system (100) according to claim 1, characterized in that the rolling elements (24) are designed as cylinders (28). 4. Cell stack system (100) according to one of the preceding claims, characterized in that the pipe system (50) extends in a longitudinal direction (52). 5. Cell stack system (100) according to one of the preceding claims, characterized in that a single section of the pipe system (50) at a fluid inlet (54) of the pipe system (50) is designed as a bellows tube (56). 6. Cell stack system (100) according to one of the preceding claims, characterized in that the pipe system (50) has at least one anode feed pipe (62), at least one cathode feed pipe (64), at least one anode discharge pipe (66) and at least one cathode discharge pipe (68), wherein each distribution system (10) has an anode feed section (122) for feeding anode feed gas (AZG) from the anode feed pipe (62) to the anode section (120), an anode discharge section (124) for discharging anode exhaust gas (AAG) from the anode section (120) to the anode discharge pipe (66), a cathode feed section (132) for feeding cathode feed gas (KZG) from the cathode feed pipe (64) to the cathode section (130) and a cathode discharge section (134) for discharging cathode exhaust gas (KAG) from the cathode section (130) to the cathode discharge pipe (68). 7. Cell stack system (100) according to one of the preceding claims, characterized in that the cell stack system (100) has a holding device fixing element (40), wherein the pipe system (50) at a pipe system fastening point (42) is mechanically firmly connected to the holding device (70) at a holding device fastening point (44) by means of the holding device fixing element (40). 8. Cell stack system (100) according to claim 7, characterized in that the pipe system (50) has a pipe system start (46), a pipe system end (48) and a pipe system length (L), and the pipe system fastening point (42) is at least 30% of the pipe system length (L), at least 35% of the pipe system length (L), at least 40% of the pipe system length (L) or at least 45% of the pipe system length (L) away from the pipe system start (46) and from the pipe system end (48). 4 sheets of drawings